Apparatus for producing cyclic pressure conditions



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APPARATUS FOR PRODUCING CYCLIC PRESSURE CONDITIONS 5 Sheets-Sheet 2 Original Filed May 25 1959 5. R H C N m m H O P. m /o ma n mul/@ Hw@ v @y m N@ a W2 .,H J Q W mmm @www

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NN NNN Aug W 1966 H. GLASCOCK ETAL 3,2693

APPARATUS FOR PRODUCING CYCLIC PRESSURE CONDITIONS 5 Sheets-Sheet 3 Original Filed May 25, 1959 5.@ RH E m@ N W V@ T me r United States Patent C) M' 3,269,383 APPARATUS FUR PRDUCING CYCLIC PRESSURE CNDiTINS Harry Glascoelr, Los Angeles, Calif. Hema-Dyna Corp., 620 E. Dyer Road, Santa Ana, Calif. 92705), and Ferdinand II. Terhaar, 4253 9th Ave., Los Angeles,

alii. Continuation of application Ser. No. 815,717, May 25, 1959. rThis application Sept. 5, 1961, Ser. No. 139,033 d Claims. (Cl. 12S-30) This application is a continuation of US. application S.N. 815,717 led May 25, 1959, and now abandoned.

This invention relates to apparatus for producing pressure and vacuum in repeated succession or cycles. The classic use for apparatus of this kind `has been for inducing respiration. However, the apparatus may .be used with any equipment for air therapy, for blood circulation equipment, reoxygenation equipment and the like.

The primary object of this invention is to provide apparatus of this character that, in a unique manner, provides effective controls for separately varying the magnitude of positive and negative pressure; the rate of cycling; Iand the rhythm of cycling, that is the relative duration of the positive and negative portions ofthe cycle.

It is another object of this invention to provide apparatus that is capable of the several adjustments above enumerated but nevertheless is essentially simple in construction.

Another object of this invention is to provide a device that is, in a unique manner, compactly arranged so that it may be accommodated in a portable carrying case.

Another object of this invention is -to provide a device of this character that incorporates certain adjustable safety features whereby the positive and negative pressures produced by the apparatus are limited.

In carrying out my invention, I use a four-Way sequence valve. This valve has two positions. In one position, the supply passage from a tan is applied to the rnotor port or output of the device while the return passage to the fan is connected to a vent port of atmosphere. In the other position, the supply passage is connected to atmosphere while the return passage is connected to the output of the device. In this manner, the source of pressure can operate continuously, and without reversal, even though the outlet conduit is subjected cyclically to conditions of pressure and vacuum. An object of this invention is to provide a simplified sequence valve structure that also, in a novel manner, is exceptionally well adapted to cooperate with the rhythm or pattern controlling device. For this purpose, the rhythm control comprises a pair of cams carried upon the output of a variable ratio-transmission mechanism. The sequence valve is of the plug-type, having cavities on opposite sides. One of the cavities continuously registers with the motor port, and cyclically registers with the supply and return passages. The other cavity continuously registers with the vent port, and cyclically registers with the return and supply passages. A rod has a rack at one end for moving the plug valve. The other lend of the rod carries two follower rollers cooperable respectively with the two cams of the rhythm adjusting mechanism. Rhythm adjustment is accomplished by changing the angular relationship of the two cams.

This invention possesses many other advantages, and has other objects which may be inade more clearly apparent from a consideration of one embodiment of the invention. For this purpose, there is shown a form in the drawings accompanying and forming a part of the pres- 3,269,335 Ice Patented August 30, 1966 ent specication. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawings:

FIGURE l is a top-plan View of the apparatus incorporating the invention, and showing the arrangement of parts in a portable carrying case, the cover panel being removed;

FIG. 2 is a vertical sectional view of the apparatus show in FIG. l, showing the arrangement of the parts, the cover panel being, however, illustrated in this iigure;

FIG. 3 is an enlarged fragmentary sectional view of the sequence valve structure, and showing specifically the arrangement of ports at the sequence valve, as well as the cam structures which serve to reciprocate the valve and also illustrating in section one of two bleeder valves;

FIG. 4 is an axial sectional view of the sequence valve, taken along plane 4-4 of FIG. 3, and illustrating the safety valve structures for limiting the applic-ation of pressure and vacuum;

FIG. 5 is a sectional view taken along a plane indicated by line 5 5 of FIG. 3;

FIG. 6 is a plan view showing that portion of the apparatus of FIG. 3 which advances and retracts the operating rack, the cams .being in a different relative adjusted position to induce a different cycle pattern;

FIG. 7 is an enlarged sectional view taken along a plane indicated by line 7 7 of FIG. 6; and

FIG. 8 is a composite graph plotting the oper-ation of the apparatus at four different relative adjusted positions iot the cams.

In FIGS. l and 2, there is illustrated a case 12 in which the apparatus is housed. The case 12 has an opening 12a closed by a control panel 11. A hinged lid may cover the panel 11 and mount a handle by the aid of which the case 12 is transported.

The cyclic pneumatic output of the apparatus is accessible at a fitting 10 that projects upwardly through an opening 11a in the panel 11 (FIG. 2). As shown in FIG. l, lugs 13 project inwardly from the fitting 10 and serve as a means for bayonet-type attachment to a conduit (not shown) that connects to the apparatus that surrounds at least a part of the body of a subject, such as the thoracic region, for controlling respiration.

A fan unit 14 serves as a course of pressure and vacuum that may be applied to the outlet fitting 1t). A motor 15 is located at the left-hand end of a housing 18. A plurality of impeller blades 17 are located at the right-hand end of the housing, and are mounted upon the shaft 16 of the motor. End plates 19 and 2li of the housing mount elbows 21 and 22 that form, respectively, supply and return ports 26 and 27 for the air circulated by the fan unit 14 as shown by the arrows in the elbows.

The housing 18 rests upon an acoustic damping pad 24 that has a cavity 25 in which the housing 18 is seated. The pad 24 in turn rests upon the bottom of the case 12.

The elbows 21 and 22 extend upwardly and connect to opposite ends of a composite valve structure.

As shown in FIG. 3, this composite structure includes two identical bleeder valve bodies 33 and 35 and a sequence valve body 23 located and supported therebetween. The outlet fitting 1t) comprises one of our tubular extensions from the body 28. Thus, the body 23 has four passages Ida, 29a, 39a, and 31a located in quadrature relationship with respect to each other and defined by four tubular extensions.

The passage a formed by the fitting 10 extends radially upwardly from a central cylindrical recess 32 of the body 28. The passage 29a extends radially downwardly from the recess 32, and constantly communicates with the interior of the case 12, or with the atmosphere, the case 12 being vented.

The passages 39a and 31a extend horizontally on opposite sides of the recess 32 and are adapted to connect to the supply and return ports 26 and 27 of the fan unit 14. The bleeder valve bodies 33 and 35 are, however, respectively interposed between the passages 39a and 31a and the elbows 21 and 22 defining the supply and return ports.

The bleeder valve body 33, for example, has two tubular fittings 33a and 33b extending in right-angle relationship with respect to each other. The fitting 33a telescopically receives the end of the fitting of the sequence valve body 28. A flexible hose 34 (see also FIG. 2) cooperates at opposite ends with the bleeder valve fitting 33b and the elbow 21 of the fan unit 14. A hose 36 similarly connects the elbow 22 to the bleeder valve body 35 which, in turn, cooperates with the tubular tting of the sequence valve body 28.

The bleeder valve bodies 33 and 35 are also secured to the panel 11 and operate in a manner to be described hereinafter.

A sequence valving device 37 (see also FIG. 4) is supported in the body 28 for movement about the horizontal axis 38 of the cylindrical recess 32. The valve 37 is in the form of a cylinder. Saddle-like recesses 39 and 40 are formed on diametrically opposite sides thereof. The

recesses 39 and 40 are formed by cylindrical cuts in the valve 37, the axes of which extend parallel to each other and in a common plane normal to the axis 38. The valve 37 is axially positioned so that the recesses 39 and 40 are capable of being moved into registry with selected pairs of the ports of the body 28.

The recess 39 continuously registers with the motor port 10a and the opposite recess 40 continuously registers with the vent port 29a. The recess 39 is capable of registry either with the port 30a or the return port 31a, while the recess 40 registers with the opposite port. The angular span of each of the recesses 39 and 40 is suicient to allow reversal of the registry.

By reciprocating the valve 37 through an angle of sixty or seventy degrees, the desired operation is achieved.

The valve device 37 as shown in FIG. 4 is contained within the cylindrical bore 32 by the aid of a pair of disklike end plates 41 and 42. The end plate 42 has a cylindrical flange 43 press-fitted within the right-hand end of the bore 32. The ange 43 is spaced inwardly from the periphery of the plate 42 whereby a stop is formed limiting inward movement of the plate. The valve 37 is annularly relieved, as at 44, to allow for entrance of the ange 43.

The closure plate 42 has a central outwardly extending hub 45 in which a sleeve bearing 46 is accommodated. The sleeve bearing 46 supports a shaft 47 to which the valve 37 is secured.

The left-hand cover plate 41 is identical to the righthand cover plate 42 except that the central hub portion 48 is enlarged to accommodate not only a sleeve bearing 49, but also a pinion 50 by the aid of which the shaft 47 may be angularly moved so that valve 37 may be shifted. The hub 48 thus has an outwardly opening recess or counterbore 51 in the bottom of which a bore 52 is formed for accommodating the sleeve bearing 49. The shaft 47 of the valve 37 projects beyond the bore 52, and its end carries the pinion 50. A rack 54 engages the pinion 50 (see FIG. 2) for purposes of rotating the valve 37. The rack 54 is accommodated in a guiding slot 55 (see also FIG. 2) in the face of the hub 48 so located that the rack 54 extends horizontally or parallel to the top panel 11. A cap 53 encloses the recess 51 as well as the slot 55 so that the rack 54 is appropriately guided. A plurality of machine screws 56 secure cap 53 in position.

The rack 54 is formed on the end of a rod 57 (FIGS. 6 and 7). The rod 57 is reciprocated by the aid of a cam and follower structure shown clearly in FIGS. 3, 6, and 7.

Upon the end of the rod 57, remote from the rack 54, a carriage 58 is attached. The carriage 58 has, at one end, a cylindrical socket 61 in which the end of the rod 57 is fitted. Set screws 62 (FIG. 6) secure the rod 57. The carriage 58 has an elongate slot 63 that parallels the rod 57. The reduced extension 64 of a shaft 65 projects through the slot 63 and thus supports the rod for reciprocatory movement. The shaft 65 continuously rotates a pair of cams 69 and 70 that serve respectively to project and retract the rod 57 and hence to reciprocate the valve 37. For purposes to appear hereinafter, the cams 69-70 form a readily replaceable cam set. The cam 69 moves the rod 57 toward the left, in a direction to cause the outlet port 10a to be subjected to pressure, and away from the position shown in FIG. 3. The cam causes the port 10a to be subjected to vacuum. Hence, the cam 70 may be referred to as the Vacuum cam, and the cam 69 may be referred to as the pressure cam.

The shaft 65 is rotated by a variable ratio-transmission mechanism 66 (see FIGS. 1, 2, and 3). The transmission mechanism 66 is mounted beneath the right-hand forward corner of the panel r11. The transmission has a control shaft 67 capable of manual rotation, and projecting through the panel 11 that serves in a suitable manner, as for example by a pinion and a gear ('FIG. 2), to adjust, through a continuous range, the speed of the shaft 65.

The pressure and vacuum cams 69 and 70 are mounted on the shaft extension `64. Thus, the cyclic rate of operation corresponding, for example, to induced breathing rate, is determined by the speed of the shaft 65. The pressure cam 69 is located between the carriage 58 and the vacuum cam 70. Thus, the pressure cam is located between the bounding planes a and b `(IFIG. 7) and the vacuum cam is located between the bounding planes b an c. The cam 70 is mounted upon the shaft 64 by the aid of a set screw 74 (FIG. 6). The cam 69 is piloted upon the shaft extension 64 and depends for its coupling thereto upon a thumb screw 74 that connects the cams together.

The thumb screw 74 has a threaded end 7,5 engaging the cam 69 at a place diametrically opposite its crest 76. The shank of the screw 74 extends through a generally arcuate slot 77 in the vacuum cam 70, the slot 7.7 being located on that portion of the cam 70 diametrically opposite its crest 78. The thumb screw 74 has an intermediate annular enlargement 79 that is capable of entering any one of four milled circular recesses 80, y81, l82, and `843 that extend along the arcuate slot 77 at the outer face of the cam 70. When the thumb screw 74 is advanced inwardly, the annular enlargement 70 engages one of the circular recesses as at 83, and a coupling of the cams -69 and 70 is achieved. Thus both cams rotate together.

The annular enlargement 79 clears the outer face of the cam '70 on movement outwardly. When so moved, the angular position of the pressure cam 69 can be adjusted relative to that of the vacuum cam 70 for a purpose presently to appear. A new position may be maintained by then advancing the thumb screw 74 until the annular enlargement 79 engages a different circular recess, as for example at 80, 81, or y82.

The manner in which the cams `69 and 70 operate may now be understood. The crests 76 and 718 of the cams 69 and 70 move about the axis of the shaft 65 and in a common circle located at 84 (FIG. 6). The follower roller 59 is positioned between the planes a and b (FIG. 7) for cooperation with the inhale cam 69 and for clearance with respect to the cam 70. The thickness of the follower 59 is slightly less than the thickness of the cam l69, to ensure clearance with the vacuum cam 70. The cam follower 59 is secured to the carriage 58 by the aid of a screw 185, the head of which is recessed within the follower 59. The cam follower 60 is secured to the Carriage on the opposite side, and is located by a spacer 88 between planesb and c for cooperation with the vacuum cam 70 and for clearance with respect to the pressure cam 69.

While the crests 76 and 78 of the cams 69 and 70 extend to the circle 84, the relieved portions of the cams are located at a smaller circle 85. The vacuum cam '70, for example, joins its relieved portion on one side by a gradual rise, as along the surface 92. An abrupt fall, as at 941, adjoins the crest 78 on the opposite side. Hence, as the vacuum cam 70 rotates in the direction of the arrow 91, it is operative to move the cam follower 60 from the inner circle 0S to the outer circle Y84. The pressure cam 69 similarly moves the follower 59.

To ensure that the dwell of the cams corresponds to a dwell in the movement of the device, the follower 59 arrives at the inner circle 85 when the spacing between the cam engaging surfaces of the followers substantially equals the sum of the radii of the circles S4 and 05.

It may be desirable from the standpoint of therapy, for example, that the time during which pressure decreases take a certain portion of the cycle, the time during which pressure increases take another portion of the cycle, and that pressure be static for the remainder of the cycle. In the present example, is allocated to pressure buildup;140% to pressure decay; and 30% to static conditions, or rest. Thus, the rise of the pressure cam 69 spans an angle of 144 and the rise of the vacuum cam 70 spans an angle of 108.

The actual slope of the cams depends first upon the characteristics of the sequence valve itself, namely, the particular relationship between pressure and angular position thereof. Secondly, the slope depends upon the desired relationship between pressure and time at the outlet of the device. By appropriately correlating the slope of the cams between the circles y85 and `34, to the characteristics of the sequence valve, the rate of rise of pressure and vacuum can be controlled. In practice, the cams 'G9-70 are provided in sets and selected sets are placed on the shaft.

It may be desirable from the standpoint of therapy to distribute the 30% dwell or rest period so that part of it follows the pressure end of the cycle and part of it follows the vacuum end of the cycle. Since the cams -69 and 70 are separate, an adjustment of their relative position serves to allocate the periods of rest in the cycle.

The arcuate slot 77 extends angularly about the shaft extension `ad a distance sufficient to permit the cams 69 and 70 to move relative to each other throughout the 30% dwell angle of 108.

In one extreme position, and shown in FIG. 6, the vacuum cam 70 begins its operation by engaging the follower ld0 immediately after the crest 76 of the pressure cam 69 engages the follower `59. This means in effect that both cams dwell after the crest 7S of the vacuum cam "70 has moved the follower to the outer circle 84. Accordingly, there is a period of dwell in the cycle before the pressure cam 69 becomes operative with respect to the follower 59.

In the graph A illustrated in FIG. 8, the travel of the rod S7 is plotted as a function of angular position of the shaft ed, the cams 69 and 70 being at the adjusted position of FIG, 6. A period of rest thus occurs between the 108 and 216 positions. The vacuum condition is thus sustained.

In the opposite extreme adjusted position of the cams 69 and 70, the pressure cam 69 becomes operative immediately after the crest of the vacuum cam 70 passes the follower 59. Thus, the entire rest period of the cycle now occurs at the end of the pressure portion of the cycle. Thus, the pressure condition is sustained. This is indicated by the graph B in FIG. 8.

The graphs C and D of FIG. 8 correspond to the two intermediate adjusted positions of the cams 69 and '70. In the graph C, two-thirds of the rest period occurs 0 after operation of the vacuum cam 70, and one-third occurs after operation of the pressure earn 69. The graph D illustrates one-third of the rest period occurring after operation of the vacuum cam 70 and two-thirds occurring after operation of the pressure cam. Thus, the angular span of the slot 77 is divided into three divisions by the four recesses 30, 81, 82, and 83, to achieve the twothirds/one-third allocations. Finer adjustments can be achieved by dividing the slot 77 into more parts. Different adjustments may be required for different purposes, and different cam sets may incorporate such differences.

The cams 69 and 70, as shown in FIG. 2, are so located that the thumb screw 74 is accessible as at a door (FIG. 1) formed in the case 12.

In addition to allocation of rest period and adjustment of the cyclic speed, there are yet two adjustments necessary to provide appropriate therapeutic control of -bodily processes. These factors are respectiveiy the magnitude of compressive pressure and the magnitude of expansive vacuum. For example, desirable induced respiration for a heart patient may be quite distinct from that for paralysis patients.

In order to provide the maximum pressure variation required, whether it be used for Vacuum or pressure output of the fan unit 14 is adjusted. This is accomplished easily by varying the speed of the motor 15, an increase in speed of the fan unit 14 resulting in an increased net positive or negative pressure, the unit 14 being of the impeller type. In order to control the speed of the motor 15, a variable ratio transformer 101 (FIGS. 1 and 2) is provided. A power cord (not shown) is mounted at a bracket 102 (FIG, 1) which is supported upon the panel 11. The cord connects via leads 103 (FIG. 2) to the primary winding of transformer 101. Inserted in the lead is a main switch 1041 (FIG. 1) mounted on the panel.

The secondary of the transformer 101 connects to the motor 15 by the aid of leads 105. By adjusting the transformer 101 as by the aid of a knob attached to a control shaft 106, the output of the fan unit 14 is adjusted.

A gauge 107 (FIG. 1) mounted on the panel 11 has a pointer 10S that reads vacuum on one side of a central zero mark 109, and pressure on the opposite side. The gauge 107 connects with the output fitting 10 by the aid of a chest 112. The chest has a tubular bracket 110 (FIG. 1) that communicates with the interior of the outlet fitting 10 at an aperture 110:1 (FIG. 3). The chest 112 serves as a means for mounting safety valves to be described hereinafter.

The gauge pointer 108 will indicate equal magnitudes of pressure and vacuum if the conduits on opposite sides of the sequence valve are identical so far as length, size, etc., are concerned. In fact, they are identical. Thus, assuming the vacuum is to be greater, the knob attached to the transformer shaft 106 is adjusted until the pointer 108 reads (during the inhale portion of the cycle) the value of vacuum desired. Now the pressure is too large, but this is diminished by the bleeder valve in the pressure line in a manner to be presently described.

If, on the contrary, the pressure is to be greater, the transformer is adjusted until the desired pressure is achieved; the vacuum is then diminished by the bleeder valve in the return line. Both bleeder valves are identical.

The body 33 in the pressure side of the apparatus has a vertical bore 112, the axis 113 of which coincides with that of the tubular fitting 33h to which the flexible hose 34 is attached. The bore 112 is reduced at its lower end to form an annular shoulder 112a. The bore intersects the opening 111-1 of the Fitting 33a.

The upper open end of the bore 112 is closed by an end cover 115. The cover 115 has a cylindrical plug 116 that telescopes within the bore 112. A shoulder 117, formed at the base of the plug, -by flange 118, abuts the edge about the upper end of the bore 112.

The upper end of the cover 115 is reduced, as at 119, to project through an aperture in the panel 11. A

threaded portion (not shown) cooperates with a nut 121 by the aid of which the cover 115 is secured in position.

A closure 111 tits in the larger portion of the bore 112. The closure includes a disk 122 located below the cover 11'5. A tubular extension 124 attached to closure 111 extends upwardly into an enlarged lower portion 125 of a through bore 126 formed in the cover 115. Extending downwardly from the disk 122 is an arcuate wall 127, the end surface of which rests upon the shoulder 112a. As shown in FIG. 5, the wall 127 has opposed edges defining a slot 128. This slot is capable of registering with a bleeder hole 129 located opposite the opening 114.

The body slot 129 may, as illustrated in FIG. 5, -be substantially closed by the cylindrical wall 127. In this position, the slot 128 of the closure 111 registers with the opening 114, and the full net positive pressure exerted by the fan unit 14 is applied to the outlet fitting 10. However, upon rotation of the closure 111, pressure is lost through the slot 129. If so, the pressure at the fitting will be reduced, depending upon the extent of by-pass to the ambient air. Thus, lby angularly moving the closure 111, the magnitude of the pressure can be reduced to a desired value. This, of course, does not affect the pressure output.

Similarly, the bleeder valve 35 operates to diminish the vacuum. As the valve 35 is opened, more and more of the available negative pressure is diminished as ambient air is sucked in.

For rotating the valve 111, a stern 111a is provided. This stem is secured to the disk 122 and it projects upwardly above the nut 121 at the panel 11. As indicated, the upper end of the stem is slotted so that a knob may be attached.

The variable speed transmission mechanism 66 for varying the cyclic rate is energized via the rnain switch 104 and a secondary switch 135. A small motor 130 (FIG. 1) so energized has an output 131 that drives the input shaft 132 to the transmission 66. For this purpose, a timing belt 133 engages timing pulleys 134 and 135 carried upon the respective shafts 131 and 132.

A pilot light 136 denotes that the main switch 104 is operated. A fuse located at a lbracket 137 may serve as a necessary link between the source of power and the electrical loads of the apparatus.

For purposes of safety, the maximum value of pressure and the maximum value of va-cuum may be limited by the aid of spring-pressed valve structures at the chest or box 112. Thus, as shown in FIG. 4, two valves 141 and 142 are provided that cooperate with apertures 143 and 144 of the wall of the box 112.

One valve 141 seats about the inside of its aperture 143, whereas the other valve 142 seats about the outside of its aperture. Stems 146 for the valves 141 and 142 respectively extend outwardly and inwardly. Springs 145 urges the valves to seat, and the pressure of seating may be adjusted by nuts 148 mounted on the stems and engaged by the springs 145.

If either the vacuum or 4pressure exceeds a value determined by the spring seating pressure exerted on the valves 141 or 142, the corresponding valve opens automatieally.

In summary, the operation of the unit is easily adjusted. The transformer is adjusted until the desired vacuum, for example, is achieved. The bleeder valve 35 is adjusted until the desired pressure is achieved. The variable ratio transmission is adjusted whereby the desired cyclic rate is achieved. Finally, replaceable cams 69 and 70 having appropriately shaped rises are adjusted to distribute the periods of rest in the cycle.

The inventors claim:

1. In pneumatic apparatus for producing alternate pressure conditions in repeated cycles, and including a pneumatic pump, means forming a supply passage and a return passage for said pump, means forming a motor port and an exhaust port for operating therapeutic appartus or the like, and a sequence valve cooperable with said passages and said ports for interconnecting the passages with the ports, said sequence valve being movable to two opposite positions, in one of which the supply passage fully registers with said motor port while said return passage fully registers with said exhaust port, and in the other of which said supply passage fully registers with said exhaust port while said return passage fully registers with said motor port, said sequence valve furthermore having transitional positions intermediate said opposite positions for gradual change in the pressure in said motor port, the combination therewith of motive means; a coupling deriving motion from said motive means and connected to said sequence valve for cyclically moving said sequence valve between said opposite positions, said coupling having means determining two transitional periods between said positions that together constitute a significant but fractional portion of the cycle, said coupling having means correspondingly determining two pause portions for the remaining fractional portion `of the cycle, said coupling including adjustable means for proportioning the relative duration of the said two pause periods while the combined duration of the transitional periods remains substantially fixed.

2. The combination as set forth in claim 1 in which said coupling comprises a pair of cams, one of the cams being moved by said motive means; angularly adjustable means mounting the other of the cams on said one cam, and a pair of followers for moving the sequence valve in lopposite directions, and both connected to said sequence valve, said followers being respectively cooperable with said cams, said followers each having a one-way driving connection with its cam whereby the return movement of each follower results only from the cam movement of the opposite followers, there being a lost motion between each cam follower and its cam during each cycle of operation, said cams having riser portions for gradually moving the followers during said transitional periods, said riser portions together being operative throughout approximately seventy percent of a cycle; and -means for adjustably determining the angular position of the cams with respect to each other thus to adjust the relative duration of the said two dwell periods.

3. The combiantion as set forth in claim 1, together with: means for adjusting through an extended range, the cyclic rate of said sequence valve; and means for varying the rate of operation of said pump to adjust its pressure output independently of said cycle rate adjustmg means.

4. An apparatus for producting cyclic gas pressure conditions, comprising a gas pump, a gas inlet line to said pump, a gas outlet line from said pump, a gas output line, a gas exhaust port, a control valve movable between two positions for selectively coupling either one of said inlet and outlet lines with said output line and the other of said inlet and outlet lines with said exhaust port, cyclical control valve operating means coupled to said valve for cyclically alternating said coupling of said inlet and outlet lines to said output line and exhaust port, and a separate adjustable bleeder valve means in each of said inlet and outlet lines for separately controlling the minimum and maximum pressures respectively therein,

H said control valve operating means including a pair of cams; means for rotating said cams in speed synchronism; means determining the .position timing of said cams; an operating rod connected to said control valve; a pair of cam followers mounted in spaced relationship on the rod and respectively in the paths of movement of said cams, one of said cam followers being positioned to be engaged by one of said cams for movement of said rod and said control valve in one direction, the other of said cam followers being positioned to be engaged by the other of said cams for movement of said rod and said control valve in the other direction, said cam followers respectively having a one-way driving connection with said cams whereby the return movement of each caml follower is effected only by cam movement of the other cam follower, there being a lost motion between each cam follower and its cam during each cycle of operation, each of ysaid cams including a dwell cam surface portion embodying a gradual transition from the dwell portion to maximum rise, position timing adjustment of said cams altering the location of the dwell periods in the operational cycle of said control valve operating means to control the relative durations of high and low pressures in said output line.

References Cited by the Examiner UNITED STATES PATENTS 2/1917 Morris 128-29 12/1939 Gunn 137-612 11/ 1941 Hammond 128-30 9/1959 Haupt 128--29 FOREIGN PATENTS 12/1951 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

C` F. ROSENBAUM, Assistant Examiner. 

1. IN PNEUMATIC APPARATUS FOR PRODUCING ALTERNATE PRESSURE CONDITIONS IN REPEATED CYCLES, AND INCLUDING A PNEUMATIC PUMP, MEANS FORMING A SUPPLY PASSAGE AND A RETURN PASSAGE FOR SAID PUMP, MEANS FORMING A MOTOR PORT AND AN EXHAUST PORT FOR OPERATING THERAPEUTIC APPARTUS OR THE LIKE, AND A SEQUENCE VALVE COOPERABLE WITH SAID PASSAGES AND SAID PORTS FOR INTERCONNECTING THE PASSAGES WITH THE PORTS, SAID SEQUENCE VALVE BEING MOVABLE TO TWO OPPOSITE POSITIONS, IN ONE OF WHICH THE SUPPLY PASSAGE FULLY REGISTERS WITH SAID MOTOR PORT WHILE SAID RETURN PASSAGE FULLY REGISTERS WITH SAID EXHAUST PORT, AND IN THE OTHER OF WHICH SAID SUPPLY PASSAGE FULLY REGISTERS WITH SAID EXHAUST PORT WHILE SAID RETURN PASSAGE FULLY REGISTERS WITH SAID MOTOR PORT, SAID SEQUENCE VALVE FURTHERMORE HAVING TRANSITIONAL POSITIONS INTERMEDIATE SAID OPPOSITE POSITIONS FOR GRADUAL CHANGE IN THE PRESSURE IN SAID MOTOR PORT, THE COMBINATION THEREWITH OF MOTIVE MEANS; A COUPLING DERIVING MOTION FROM SAID MOTIVE MEANS AND CONNECTED TO SAID SEQUENCE VALVE FOR CYCLICALLY MOVING SAID SEQUENCE VALVE BETWEEN SAID OPPOSITE POSITIONS, SAID COUPLING HAVING MEANS DETERMINING TWO TRANSITIONAL PERIODS BETWEEN SAID POSITIONS THAT TOGETHER CONSTITUTE A SIGNIFICANT BUT FRICTIONAL PORTION OF THE CYCLE, SAID COUPLING HAVING MEANS CORRESPONDING DETERMINING TWO PAUSE PORTIONS FOR THE REMAINING FRACTIONAL PORTION OF THE CYCLE, SAID COUPLING INCLUDING ADJUSTABLE MEANS FOR PROPORTIONING THE RELATIVE DURATION OF THE SAID TWO PAUSE PERIODS WHILE THE COMBINED DURATION OF THE TRANSITIONAL PERIODS REMAINS SUBSTANTIAL FIXED. 